In the manufacturing process of a semiconductor device, an SOD (Spin on Dielectric) method is employed as one of the technologies for forming an insulating film (an interlayer insulating film) on a semiconductor wafer. In the SOD method, a coating film, i.e., a film formed by the coating method, is formed on a wafer by a spin coating method, followed by applying a chemical processing or a heat processing or the like to the coating film so as to form an insulating film. To be more specific, the surface of a wafer is coated first with a chemical liquid prepared by dispersing the material for forming the insulating film in a solvent, followed by evaporating the solvent from the coating film so as to dry the coating film. Then, a baking processing is applied to the dried coating film so as to cause a chemical reaction to be brought about by the heating. Finally, the coating film is heated for the curing purpose, thereby obtaining a desired insulating film. Incidentally, depending on the kind of the chemical liquid used, it is necessary to apply an additional processing such as the processing under an ammonia gas atmosphere or a chemical processing such as a solvent exchange processing.
An SOD system 400 shown in FIG. 35 and an SOD system 450 shown in FIG. 36 are known to the art as the SOD system for carrying out the processing described above.
In the SOD system 400 shown in FIG. 35, a carrier 410 housing, for example, 25 wafers is transferred into a carrier stage 411. The wafers within the carrier 410 are taken out by a delivery arm 412 and, then, transferred into a process zone 414 through the delivery section of a shelf unit 413a. A transfer mechanism 415 for transferring the wafer is arranged in the central portion of the process zone 414. Also, a plurality of shelf units, e.g., two shelf units 413b and 423c, and a plurality of coating units 416 for coating the wafer with a chemical liquid are arranged in the vicinity of the transfer mechanism 415. Each of the shelf units 413b and 413c noted above includes a plurality of process units such as heating units for applying a prescribed heat processing to the wafer. The transfer mechanism 415 serves to transfer the wafer into and out of these process units. Incidentally, the heating unit noted above includes, for example, a baking unit for performing a baking processing and a low temperature heating unit for applying a drying processing to the chemical liquid.
It should be noted that various kinds of chemical liquids are used in the SOD method and, thus, the process conditions of the SOD method are rendered slightly different in many cases depending on the kind of the chemical liquid used. For example, the heat processing under a low temperature is required, or it is necessary to carry out the processing under a different processing atmosphere. Such being the situation, it is necessary in some cases to change the specifications of the coating unit and the heating unit depending on the kind of the chemical liquid used. Also, even in the case of using the same chemical liquid, it is necessary in some cases to change the process conditions depending on the desired thickness of the film that is to be formed. In view of the variety of the chemical liquids described above, it is not advisable in terms of the cost and the footprint to newly prepare a system in accordance with the change in process.
Under the circumstances, vigorous research is being conducted by the present inventors in an attempt to develop an SOD system capable of coping with various processes. For example, disclosed in Japanese Patent Disclosure (Kokai) No. 2000-138213 is an SOD system in which a cooling unit, a coating unit, an aging unit, a solvent exchange unit, a curing unit, and a heating unit are arranged in the process section for applying a series of processing to a substrate.
In the SOD system disclosed in the Japanese patent document quoted above, the cooling unit, the aging unit, the curing unit, and the heating unit are stacked one upon the other so as to form a process unit group of a multi-stage structure. On the other hand, the coating unit and the solvent exchange unit are arranged separately from the process unit group.
However, if a plurality of process units are arranged in a dispersed fashion as in the SOD system quoted above, the footprint of the entire SOD system is increased. Also, the transfer efficiency of the wafer within the SOD system is rendered poor so as to lower the through-put. Further, a difficulty is generated in the SOD system quoted above in performing various automatic controls. It should be noted in this connection that the wafer is coated with a chemical liquid in the coating unit and a prescribed heat processing is applied to the coating film in the baking unit, followed by measuring the thickness of the coating film. If various automatic controls are to be performed on the basis of the measured data so as to change the process parameters in the coating unit and the baking unit and to generate an alarm when the thickness of the coating film exceeds a prescribed range, it is difficult to locate the process unit causing the inconvenience. It is also difficult to supervise the entire apparatus. Still further, where a certain process unit is in trouble, it is necessary to stop all the processing in the SOD system for coping with the process unit that is in trouble, with the result that the productivity is lowered.
The SOD system 450 shown in FIG. 36 is described in detail in Japanese Patent Disclosure No. 2003-100621. The SOD system 450 comprises a first process zone 460A. Also, a second process zone 460B and a carrier station 460C are arranged to have the first process zone 460A sandwiched therebetween.
The first process zone 460A includes a plurality of coating units 461 for coating a wafer with a chemical liquid so as to form a coating film. These coating units 461 are stacked one upon the other so as to form a multi-stage structure. In the coating unit 461, a chemical liquid is supplied from a nozzle onto substantially the center of rotation of a wafer held by a spin chuck. In accordance with rotation of the spin chuck, the chemical liquid supplied onto the wafer is spread on the wafer surface so as to form a coating film. The first process zone 460A also includes shelf units 462a and 462b. Each of these shelf units 462a and 462b is of a multi-stage structure including, for example, a temperature control unit for controlling the wafer at a prescribed temperature, a delivery unit, and a low temperature heating unit for heating the wafer having the coating film formed thereon so as to dry the coating film. The process units noted above are stacked one upon the other so as to form each of the shelf units 462a and 462b. The wafer is transferred into and out of each of these process units by a transfer mechanism 463.
The second process zone 460B includes two shelf units 464a and 464b of a heating system. In each of these shelf units 464a and 464b, a baking unit for baking the wafer after the drying processing at a higher temperature and a curing unit for further heating the baked wafer for curing the coating film are stacked one upon the other so as to form a multi-stage structure. The wafer is transferred into and out of the process unit included in each of these shelf units 464a and 464b by a transfer mechanism 465.
The carrier station 460C includes a table section 466 on which is disposed a carrier 470 housing a large number of wafers. The carrier station 460 also includes a delivery arm 467 for transferring the wafer between the carrier 470 and the first process zone 460A.
In the SOD system 450, the coating unit 461 and the temperature control unit are arranged in a process zone differing from that of the baking unit and the curing unit, as in the SOD system 400 shown in FIG. 35. In addition, the coating unit 461 and the temperature control unit are arranged in a dispersed fashion within the same process zone. It follows that the footprint is also increased in the SOD system 450. Also, since the process units are arranged in a dispersed fashion in the SOD system 450, the transfer efficiency of the wafer is made poor so as to lower the through-put.
Further, in the SOD system 450, the plural coating units 461 are stacked one upon the other within the same shelf unit so as to form a multi-stage structure. As a result, a drain pipe 469 for recovering the waste chemical liquid discharged from the coating units 461 includes a horizontal portion as schematically shown in FIG. 37. The waste chemical liquid discharged from the plural coating units 461 fails to flow smoothly within the horizontal portion of the drain pipe 469 and tends to stagnate within the horizontal portion. Since the chemical liquid used in the SOD system tends to be solidified, a serious problem is generated that the horizontal portion of the drain pipe 469 is plugged with the waste chemical liquid.
It should also be noted that, since the coating units 461 are arranged side by side and stacked one upon the other, it is necessary to change the construction of the pipes such as the drain pipe 469 for each of the coating units 461. What should be noted in this connection is that the manufacturing process of the SOD system is made complex by the dispersion of the specification of the piping so as to give rise to the problem that the productivity is lowered.
It should also be noted that a chemical liquid tank for storing the chemical liquid is arranged in a region (not shown) different from the region in which the coating unit 461 is arranged, with the result that the supply path of the chemical liquid is prolonged. A cleaning processing is applied to the coating unit 461 after completion of the processing of a prescribed lot. Since the chemical liquid is not discharged from the nozzle during the cleaning processing of the coating unit 461, the cleaning processing is carried out under the state that the chemical liquid is left to remain within the supply path. When the processing of the succeeding lot is started, a dummy dispensing is carried out such that all the chemical liquid remaining inside the supply path is discharged from the supply nozzle. Therefore, it is necessary to discharge as a waste material a large amount of the chemical liquid remaining inside the supply path, leading to an increased process cost.
Further, in replacing the chemical liquid tank or in replacing, for example, the chemical liquid filter connected to the chemical liquid pipe, bubbles of the chemical liquid are generated within the pipe. Naturally, it is necessary to remove the bubbles before the coating operation for forming a coating film on the substrate surface. A large amount of the chemical liquid must be discarded during the operation for removing the bubbles, if the pipe is long.